CN117638154A - Fuel cell system - Google Patents

Fuel cell system Download PDF

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Publication number
CN117638154A
CN117638154A CN202310662306.2A CN202310662306A CN117638154A CN 117638154 A CN117638154 A CN 117638154A CN 202310662306 A CN202310662306 A CN 202310662306A CN 117638154 A CN117638154 A CN 117638154A
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CN
China
Prior art keywords
fuel cell
cell stack
gas
flow rate
cell stacks
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Pending
Application number
CN202310662306.2A
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Chinese (zh)
Inventor
小关真弘
森裕晃
深见竜也
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Toyota Motor Corp
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Toyota Motor Corp
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Publication date
Application filed by Toyota Motor Corp filed Critical Toyota Motor Corp
Publication of CN117638154A publication Critical patent/CN117638154A/en
Pending legal-status Critical Current

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/04—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids
    • H01M8/04082—Arrangements for control of reactant parameters, e.g. pressure or concentration
    • H01M8/04089—Arrangements for control of reactant parameters, e.g. pressure or concentration of gaseous reactants
    • H01M8/04119—Arrangements for control of reactant parameters, e.g. pressure or concentration of gaseous reactants with simultaneous supply or evacuation of electrolyte; Humidifying or dehumidifying
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/04—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids
    • H01M8/04223—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids during start-up or shut-down; Depolarisation or activation, e.g. purging; Means for short-circuiting defective fuel cells
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/04—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids
    • H01M8/04223—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids during start-up or shut-down; Depolarisation or activation, e.g. purging; Means for short-circuiting defective fuel cells
    • H01M8/04228—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids during start-up or shut-down; Depolarisation or activation, e.g. purging; Means for short-circuiting defective fuel cells during shut-down
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/04—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids
    • H01M8/04298—Processes for controlling fuel cells or fuel cell systems
    • H01M8/043—Processes for controlling fuel cells or fuel cell systems applied during specific periods
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/04—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids
    • H01M8/04298—Processes for controlling fuel cells or fuel cell systems
    • H01M8/043—Processes for controlling fuel cells or fuel cell systems applied during specific periods
    • H01M8/04303—Processes for controlling fuel cells or fuel cell systems applied during specific periods applied during shut-down
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/04—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids
    • H01M8/04298—Processes for controlling fuel cells or fuel cell systems
    • H01M8/04313—Processes for controlling fuel cells or fuel cell systems characterised by the detection or assessment of variables; characterised by the detection or assessment of failure or abnormal function
    • H01M8/0432—Temperature; Ambient temperature
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/04—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids
    • H01M8/04298—Processes for controlling fuel cells or fuel cell systems
    • H01M8/04313—Processes for controlling fuel cells or fuel cell systems characterised by the detection or assessment of variables; characterised by the detection or assessment of failure or abnormal function
    • H01M8/0438—Pressure; Ambient pressure; Flow
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/04—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids
    • H01M8/04298—Processes for controlling fuel cells or fuel cell systems
    • H01M8/04313—Processes for controlling fuel cells or fuel cell systems characterised by the detection or assessment of variables; characterised by the detection or assessment of failure or abnormal function
    • H01M8/04492—Humidity; Ambient humidity; Water content
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/04—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids
    • H01M8/04298—Processes for controlling fuel cells or fuel cell systems
    • H01M8/04313—Processes for controlling fuel cells or fuel cell systems characterised by the detection or assessment of variables; characterised by the detection or assessment of failure or abnormal function
    • H01M8/04537—Electric variables
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/04—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids
    • H01M8/04298—Processes for controlling fuel cells or fuel cell systems
    • H01M8/04694—Processes for controlling fuel cells or fuel cell systems characterised by variables to be controlled
    • H01M8/04746—Pressure; Flow
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/04—Auxiliary arrangements, e.g. for control of pressure or for circulation of fluids
    • H01M8/04298—Processes for controlling fuel cells or fuel cell systems
    • H01M8/04694—Processes for controlling fuel cells or fuel cell systems characterised by variables to be controlled
    • H01M8/04858—Electric variables
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/24—Grouping of fuel cells, e.g. stacking of fuel cells
    • H01M8/249—Grouping of fuel cells, e.g. stacking of fuel cells comprising two or more groupings of fuel cells, e.g. modular assemblies
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/30—Hydrogen technology
    • Y02E60/50—Fuel cells

Abstract

The present invention relates to a fuel cell system. The fuel cell system includes a plurality of fuel cell stacks, a gas supply unit, an impedance detection unit, and a control device. The control device is configured to perform a water discharge process in which, when power generation of the fuel cell stack is stopped, gas is supplied to the fuel cell stack to discharge water remaining in the fuel cell stack. The drainage treatment includes: for a fuel cell stack in which a detected value in the fuel cell stacks reaches a predetermined value, a transport flow rate of the gas is restricted until the detected value reaches the predetermined value at all the fuel cell stacks.

Description

Fuel cell system
Technical Field
The technology disclosed in this specification relates to a fuel cell system.
Background
In the fuel cell system, when the power generation of the fuel cell stack is stopped, water generated by the chemical reaction remains in the fuel cell stack. When this residual water remains in the fuel cell stack, the residual water may freeze moderately in a low-temperature environment such as a temperature below freezing point, and the fuel cell stack may not operate normally.
In this connection, japanese unexamined patent application publication No.2021-180160 (JP 2021-180160A) describes a fuel cell system in which, when power generation of a fuel cell stack is stopped, a water discharge process of delivering an oxidant gas to the fuel cell stack to discharge water remaining in the fuel cell stack is performed. At this time, the amount of residual water in the fuel cell stack is determined based on the impedance of the fuel cell stack.
Disclosure of Invention
When a plurality of fuel cell stacks are electrically connected in series, it is preferable from the viewpoint of operation control to terminate the water discharge process of all the fuel cell stacks at the same time. However, the drainage treatment of the fuel cell stack is rarely completed at the same time, and there is generally a difference in the time at which the drainage treatment is completed. In this case, terminating the water drain process when the water drain of some of the fuel cell stacks is completed will cause residual water to remain in the remaining fuel cell stacks. In addition, continuing the water discharge processing until all the fuel cell stacks are completely discharged will cause the water discharge processing to be performed beyond that necessary for the fuel cell stacks that have completed the water discharge.
In view of the above, the present specification provides a technique for reducing the difference in the amount of residual water in each fuel cell stack to a relatively low level even when the water discharge processes of the fuel cell stacks are simultaneously terminated.
The technology disclosed in this specification is presented as a fuel cell system. In a first aspect thereof, a fuel cell system includes: a plurality of fuel cell stacks electrically connected in series; a gas supply unit that supplies gas to the fuel cell stack; an impedance detection unit that detects an impedance of the fuel cell stack; and a control device that controls the operation of the fuel cell stack and the gas supply unit and obtains the detection value detected by the impedance detection unit. The control device is configured to perform a water discharge process in which, when power generation of the fuel cell stack is stopped, gas is supplied to the fuel cell stack to discharge water remaining in the fuel cell stack. The drainage treatment includes: for the fuel cell stack in which the detected value in the fuel cell stack reaches a predetermined value, the delivery flow rate of the gas is restricted until the detected value reaches the predetermined value at all the fuel cell stacks.
In the above-described fuel cell system, the control device monitors the impedance of each fuel cell stack during the drain treatment. The smaller the amount of residual water in the fuel cell stack, the higher the impedance detected with respect to the fuel cell stack. Therefore, the amount of residual water may be considered to be relatively small inside the fuel cell stack in which the impedance of not less than the predetermined value is detected, and the amount of residual water may be considered to be relatively large inside the fuel cell stack in which the impedance of less than the predetermined value is detected. Therefore, in the water discharge process according to the present technology, the transport flow rate of the gas is restricted for the fuel cell stacks whose impedance has reached a predetermined value until the impedance reaches a predetermined value for all the fuel cell stacks. Such a configuration enables the amount of residual water in all fuel cell stacks during the drain treatment to be equalized. Accordingly, the water discharge process without limitation of the transport flow rate of the gas for each of the fuel cell stacks can be continued, so that the water discharge processes of the plurality of fuel cell stacks are terminated simultaneously, and thus the difference in the amount of residual water in each fuel cell stack can be made relatively small.
According to the second aspect, in the first aspect, the drainage process may further include correcting the transport flow rate of the gas according to the temperature of the fuel cell stack. The amount of discharged water in the fuel cell stack varies according to the amount of saturated water vapor depending on the temperature of the fuel cell stack, in addition to the flow rate of the gas supplied to the fuel cell stack. Therefore, correcting the transport flow rate of the gas for each fuel cell stack in accordance with the temperature of each fuel cell stack makes it possible to eliminate the difference in the amount of residual water in each fuel cell stack in a relatively short period of time.
According to a third aspect, in the first or second aspect, the gas may be an oxidant gas supplied to a cathode side of the fuel cell stack. In a fuel cell stack, water is mainly produced by chemical reaction of gases on the cathode side. Accordingly, the drainage treatment is performed using the oxidant gas supplied to the cathode side of the fuel cell stack, and the residual water in the fuel cell stack can be efficiently discharged to the outside.
According to a fourth aspect, in the first to third aspects, the gas supply unit may include, for each of the fuel cell stacks: an oxidant gas supply path connected to a supply port of the fuel cell stack and including a compressor; an oxidant gas exhaust path connected to an exhaust port of the fuel cell stack; and a shunt path that connects the oxidant gas supply path and the oxidant gas discharge path to each other, and that includes a shunt valve. In this case, limiting the flow rate of the oxidizer gas in the drainage process may include opening a diverting valve to detour the oxidizer gas from the diverting path to the oxidizer gas discharge path. According to such a configuration, the flow rate of the oxidizer gas supplied to the fuel cell stack can be adjusted without accurately controlling the operation of the compressor.
In addition to or alternatively to the above, limiting the flow rate of the oxidant gas in the drainage process may include limiting the flow rate of the oxidant gas delivered by the compressor. According to such a configuration, the supply amount of the oxidant gas supplied to the fuel cell unit can be adjusted regardless of the presence or absence of the above-described split flow path.
Drawings
Features, advantages, and technical and industrial significance of exemplary embodiments of the present invention will be described below with reference to the accompanying drawings, in which like reference numerals denote like elements, and in which:
fig. 1 is a circuit diagram including a fuel cell system 10 according to one embodiment;
fig. 2 is a diagram schematically illustrating the configuration of the fuel cell system 10 according to the embodiment;
fig. 3 is a flowchart for describing the water discharge process performed by the control device 70, wherein Imp (a) represents the impedance of the first fuel cell stack 22A, and Imp (B) represents the impedance of the second fuel cell stack 22B;
fig. 4A is a diagram showing an example of the impedance of the first fuel cell stack 22A of the first fuel cell unit 20A, the delivery flow rate of air, and the opening degrees of the inlet valve 36, the split valve 40, and the outlet valve 44;
fig. 4B is a diagram showing an example of the impedance of the second fuel cell stack 22B of the second fuel cell unit 20B, the delivery flow rate of air, and the opening degrees of the inlet valve 36, the split valve 40, and the outlet valve 44;
fig. 5 is a diagram for describing a relationship between the amount of residual water in the fuel cell stack 22 and impedance;
fig. 6A is a diagram for describing an example of the delivery flow rate of air during the correction of the drainage treatment according to the temperature of the fuel cell stacks 22A and 22B, wherein fig. 6A corresponds to fig. 4A; and is also provided with
Fig. 6B is a diagram for describing an example of the transport flow rate of air during the correction of the drain treatment according to the temperature of the fuel cell stacks 22A and 22B, wherein fig. 6B corresponds to fig. 4B, and the transport flow rate of air of fig. 4B has been corrected.
Detailed Description
A fuel cell system 10 according to an embodiment will be described with reference to the accompanying drawings. The fuel cell system 10 according to the present embodiment is mainly mounted in a large fuel cell electric vehicle (e.g., an automobile, a bus, a truck, and a train), a stationary fuel cell device, and the like. Note that the fuel cell system 10 may also be mounted in various types of moving objects other than vehicles (e.g., ships and airplanes).
As illustrated in fig. 1 and 2, the fuel cell system 10 includes a plurality of fuel cell units 20 and a control device 70 that controls the operation of these fuel cell units 20. The fuel cell unit 20 includes a first fuel cell unit 20A and a second fuel cell unit 20B. Note that the number of the fuel cell units 20 included in the fuel cell system 10 is not particularly limited. In another embodiment, the number of fuel cell units 20 may be three or more.
As illustrated in fig. 1 and 2, each fuel cell unit 20 includes a fuel cell stack 22, an oxidant gas supply unit 30, a fuel gas supply unit 50, and a cell monitor 60. The fuel cell stack 22 of the first fuel cell unit 20A and the fuel cell stack 22 of the second fuel cell unit 20B are electrically connected in series. Hereinafter, the fuel cell stack 22 of the first fuel cell unit 20A may be simply referred to as "first fuel cell stack 22A", and the fuel cell stack 22 of the second fuel cell unit 20B may be simply referred to as "second fuel cell stack 22B".
The two fuel cell stacks 22 connected in series are connected to the storage battery 104 via a Direct Current (DC) -DC converter 102, and supply electric power to the storage battery 104, but are not particularly limited thereto. The battery 104 has a plurality of secondary battery cells built in, and is configured to be able to be charged repeatedly by external power. The DC-DC converter 102 is a converter that boosts electric power and controls electric power transmitted between the two fuel cell stacks 22 and the storage battery 104. The two fuel cell stacks 22 are also connected to a load 108 via a Power Control Unit (PCU) 106, and supply electric power to the load 108. The PCU 106 has a built-in DC-DC converter and/or inverter, and controls the power transmitted between the two fuel cell stacks 22 and the load 108. Similarly, battery 104 is also connected to load 108 via PCU 106 and supplies power to load 108. The operation of the two fuel cell stacks 22 is monitored and controlled by the control device 70, which will be described in detail later.
As illustrated in fig. 2, each of the fuel cell stacks 22 has a structure in which a plurality of fuel cell cells 24 are stacked. The fuel cell stack 22 generates electricity by chemical reaction of the oxidant gas and the fuel gas within the fuel cell 24. In the fuel cell unit 20 according to the present embodiment, air is used as the oxidant gas supplied to the cathode side, and hydrogen gas is used as the fuel gas supplied to the anode side. That is, in the present embodiment, air is an example of an oxidizer gas, and hydrogen is an example of a fuel gas.
Note that the specific configuration of the fuel cell electric core 24 is not particularly limited. Each of the fuel cell cells 24 includes, for example, a membrane electrode and gas diffusion layer assembly (MEGA), an anode-side separator, a cathode-side separator, and a support frame, although omitted from illustration. The membrane electrode and the gas diffusion layer assembly are manufactured by sequentially laminating an anode-side gas diffusion layer, an anode electrode, an electrolyte membrane, a cathode electrode, and a cathode-side gas diffusion layer.
As illustrated in fig. 2, the oxidant gas supply unit 30 is a unit for supplying the oxidant gas (air) to the fuel cell stack 22. The oxidizer gas supply unit 30 includes a compressor 32, an oxidizer gas supply path 34, an inlet valve 36, a split path 38, a split valve 40, an oxidizer gas discharge path 42, and an outlet valve 44.
The compressor 32 is disposed in the oxidant gas supply path 34. The oxidant gas supply path 34 is connected to the cathode side supply port 26 of the fuel cell stack 22. A cathode side supply port 26 of the fuel cell stack 22 is connected to each of the fuel cell cells 24 within the fuel cell stack 22. Air compressed by the compressor 32 is supplied to the cathode-side supply port 26 of the fuel cell stack 22 through the oxidant gas supply path 34. An inlet valve 36 is provided on the oxidant gas supply path 34. Note that the oxidizer gas supply unit 30 may also include an intercooler that cools air that is warmed up due to compression by the compressor 32, but is not particularly limited thereto.
The oxidant gas exhaust path 42 is connected to the cathode side exhaust port 27 of the fuel cell stack 22. A cathode side exhaust port 27 of the fuel cell stack 22 is connected to each of the fuel cell cells 24 within the fuel cell stack 22. After the reaction within the fuel cell stack 22, the air that has passed through the fuel cell cells 24 is discharged from the fuel cell stack 22 to the oxidant gas discharge path 42 through the cathode side discharge port 27. An outlet valve 44 is provided on the oxidizer gas discharge path 42. An outlet valve 44, also referred to as a back pressure valve, adjusts the delivery flow rate of the oxidant gas supplied to the fuel cell stack 22 together with the flow dividing valve 40.
The shunt path 38 connects the oxidant gas supply path 34 and the oxidant gas exhaust path 42 to each other. A diverter valve 40 is disposed on the diverter path 38. According to the opening and closing of the flow dividing valve 40 and the outlet valve 44, a part or all of the air flowing on the oxidant gas supply path 34 is sent to the oxidant gas exhaust path 42 through the flow dividing path 38 without being supplied to the fuel cell stack 22. Accordingly, the delivery flow rate of the oxidant gas supplied to the fuel cell stack 22 is adjusted. Note that the inlet valve 36 is positioned downstream of the branching position of the oxidant gas supply path 34 and the branching path 38, and the outlet valve 44 is positioned upstream of the junction of the oxidant gas discharge path 42 and the branching path 38.
As illustrated in fig. 2, the fuel gas supply unit 50 is a unit for supplying fuel gas (hydrogen gas) to the fuel cell stack 22. The fuel gas supply unit 50 includes a fuel gas tank 52, a fuel gas supply path 54, a supply control valve 56, and a fuel gas discharge path 58. The fuel gas tank 52 stores hydrogen gas. The fuel gas tank 52 is connected to the anode-side supply port 28 of the fuel cell stack 22 via a fuel gas supply path 54. An anode side supply port 28 of the fuel cell stack 22 is connected to each of the fuel cell cells 24 within the fuel cell stack 22. The supply control valve 56 is provided on the fuel gas supply path 54. Opening of the supply control valve 56 causes the hydrogen gas supplied from the fuel gas tank 52 to pass through the fuel gas supply path 54 and be supplied to the anode-side supply port 28 of the fuel cell stack 22.
The anode-side exhaust path 29 of the fuel cell stack 22 is connected to the fuel gas exhaust port 58. An anode side exhaust port 29 of the fuel cell stack 22 is connected to each of the fuel cell cells 24 within the fuel cell stack 22. The hydrogen gas that has flowed into the fuel cell stack 22 is discharged from the fuel gas discharge path 58 to the outside through the anode-side discharge port 29. At this time, the gas discharged from the fuel cell stack 22 to the outside may contain unreacted hydrogen. Accordingly, each fuel cell unit 20 may further include a recirculation path (omitted from the illustration) so that unreacted hydrogen gas may be recirculated to the fuel cell stack 22.
As illustrated in fig. 2, a cell monitor 60 is disposed inside the fuel cell stack 22 and is electrically connected to the fuel cell cells 24. The cell monitor 60 outputs a voltage signal for detecting the voltage of each fuel cell 24. The voltage signal output by the cell monitor 60 is input to the control device 70, and is used for a process of calculating the impedance of the fuel cell 24, details of which will be described later.
As illustrated in fig. 1 and 2, the control device 70 is a computer device having a processor, a memory, and the like. The control device 70 is communicatively connected to each of the fuel cell stacks 22, and in particular to each of the compressor 32, the inlet valve 36, the diverter valve 40, the outlet valve 44, and the supply control valve 56 of the fuel gas supply unit 50 of the oxidant gas supply unit 30, and is capable of controlling and monitoring the operation thereof. The control device 70 calculates the request power to be requested for the fuel cell stack 22 based on the external power request. Based on the calculated requested power, the control device 70 controls the operation of each of the compressor 32, the inlet valve 36, the flow dividing valve 40, the outlet valve 44, and the supply control valve 56. Accordingly, the air pressure and the hydrogen pressure supplied to the fuel cell stack 22 are controlled, and the electric power output from the fuel cell stack 22 is regulated to the above-described request electric power. As described above, the voltage signal of the cell monitor 60 is input to the control device 70. In addition, the control device 70 monitors the output current of the fuel cell stack 22. The control device 70 is capable of calculating the impedance of the fuel cell cells 24 based on the voltage signal from the cell monitor 60 and the output current of the fuel cell stack 22. Now, the cell monitor 60 and a part of the control device 70 according to the present specification are examples of the impedance detection unit according to the present technology. Note that the control device 70 may be composed of a single computer device, or may be composed of a combination of a plurality of computer devices.
The control device 70 is configured to be able to perform a drainage process. When the power generation of the plurality of fuel cell stacks 22 is stopped, the water discharge process is mainly performed. In the water discharge process, a gas (here, air) is supplied to the fuel cell stack 22 so as to discharge water remaining in the fuel cell stack 22.
The drainage process performed by the control device 70 will be described with reference to fig. 3 to 5. At the start of the water discharge process (start in fig. 3), the control device 70 operates the compressor 32 of each fuel cell unit 20. The control device 70 also opens the inlet valve 36 and the outlet valve 44 and closes the diverter valve 40 (time 0 in fig. 4A and 4B). As an example, as shown in fig. 4A and 4B, in each of the fuel cell units 20A and 20B, the opening degrees of the inlet valve 36 and the outlet valve 44 are 100%, and the opening degree of the split valve 40 is 0%. At this time, in each fuel cell unit 20, all the air that has been compressed by the compressor 32 and has flowed into the oxidant gas supply path 34 flows into the fuel cell stack 22. Then, the air that has passed through the fuel cell stack 22 is discharged to the outside through the oxidizer gas discharging path 42 together with the residual water present in the fuel cell stack 22. At this time, the transport flow rate GA of the air that is transported to the first fuel cell stack 22A (hereinafter, may be referred to as "first transport flow rate GA") and the transport flow rate GB of the air that is transported to the second fuel cell stack 22B (hereinafter, may be referred to as "second transport flow rate GB") are each a predetermined standard flow rate N.
Then, the control device 70 determines whether the impedance of the first fuel cell stack 22A is not less than a predetermined value PV (step S10). The predetermined value PV may now be a value determined by experiment, or may be a value determined by simulation or the like. As an example, in the graph in fig. 5 showing the relationship between the amount of residual water in the fuel cell stack 22 and the impedance of the fuel cell stack 22, the predetermined value PV employed may be the impedance when the gradient of the graph greatly changes. For example, the predetermined value PV employed may be an impedance at which the impedance of the fuel cell stack 22 starts to vary relatively greatly with respect to the amount of variation in the amount of residual water in the fuel cell stack 22. Note that in still another embodiment, the predetermined value PV may be determined according to the influence of factors other than the amount of residual water in the fuel cell stack 22 on the impedance. In addition, power generation of the fuel cell stack 22 is necessary for impedance measurement. The air is delivered to the fuel cell stack 22 using the electric power generated by the power generation.
When step S10 returns to no, it is assumed that the amount of residual water in the first fuel cell stack 22A is relatively large, and the drainage process progresses relatively slowly. In contrast, when step S10 returns yes, it is assumed that the amount of residual water in the first fuel cell stack 22A is relatively small, and the drainage process progresses relatively quickly.
At the beginning of the water discharge process in fig. 3, the amount of residual water in each fuel cell stack 22 is relatively large, and therefore it is considered that the impedance of the first fuel cell stack 22A will be smaller than the predetermined value PV, that is, no will be returned in step S10. In this case, the control device 70 then determines whether the impedance of the second fuel cell stack 22B is not less than a predetermined value PV (step S12). The predetermined value PV in step S12 is equal to the predetermined value PV in step S10. As described above, at the beginning of the water discharge process in fig. 3, the amount of residual water in each fuel cell stack 22 is relatively large, and therefore it is considered that the impedance of the second fuel cell stack 22B will also be smaller than the predetermined value PV, that is, no will also be returned in step S12.
When "no" is returned in step S10 and "no" is returned in step S12, the control device 70 maintains the first transport flow rate GA and the second transport flow rate GB at the above-described standard flow rate N (step S14). That is, the control device 70 maintains the opening degrees of the inlet valve 36 and the outlet valve 44 at 100% and the opening degree of the flow dividing valve 40 at 0% in each of the fuel cell units 20A and 20B (from time 0 to time T1 in fig. 4A and 4B). Accordingly, the drainage treatment of the fuel cell stacks 22A and 22B progresses.
Then, the control device 70 determines whether or not the termination condition is satisfied (step S16). The termination condition here includes that neither the impedance of the first fuel cell stack 22A nor the impedance of the second fuel cell stack 22B is less than the termination value FV. The termination value FV is an impedance value that allows termination of the water discharge treatment of the fuel cell stack 22, and is a value that is greater than the predetermined value PV. As an example, as shown in fig. 5, an impedance value corresponding to the amount of residual water in the fuel cell stack 22 becoming substantially zero may be employed as the termination value FV. When "no" is returned in step S16, the control device 70 returns to the process of step S10.
As the drainage treatment progresses in the fuel cell stacks 22A and 22B, the degree of progress of the drainage treatment may differ therebetween. For example, the drainage treatment of the first fuel cell stack 22A may progress relatively quickly, and the drainage treatment of the second fuel cell stack 22B may progress relatively slowly. In this case, only the impedance of the first fuel cell stack 22A will reach the predetermined value PV (yes in step S10 and no in step S20).
When "yes" is returned in step S10 and "no" is returned in step S20, control device 70 limits the first transport flow rate GA to first fuel cell stack 22A to a predetermined limiting flow rate n (step S22). The restricted flow rate N is a value smaller than the standard flow rate N, and its specific value is not particularly limited. On the other hand, the second transport flow rate GB to the second fuel cell stack 22B is maintained at the standard flow rate N. Thus, the first transport flow rate GA is smaller than the second transport flow rate GB. In the first fuel cell unit 20A, the control device 70 limits the delivery flow rate of the air by the compressor 32 and/or changes the opening degrees of the outlet valve 44 and the split valve 40, whereby the first delivery flow rate GA can be adjusted to the limiting flow rate n.
As an example, the control device 70 according to the present embodiment increases the opening degree of the split valve 40 to a predetermined split opening degree (for example, 80%) and decreases the opening degree of the outlet valve 44 to a predetermined limiting opening degree (for example, 20%) at the first fuel cell unit 20A (time T1 in fig. 4A and 4B). On the other hand, in the second fuel cell unit 20B, the opening degrees of the inlet valve 36 and the outlet valve 44 are maintained at 100%, and the opening degree of the split valve 40 is maintained at 0%. As a result, in the first fuel cell unit 20A, a portion of the air compressed by the compressor 32 flows into the oxidizer gas discharge path 42 via the split flow path 38. That is, the delivery flow rate of the air delivered to the first fuel cell stack 22A is limited. Therefore, in the first fuel cell unit 20A, the first transport flow rate GA is restricted by opening the split valve 40 to detour the air from the split path 38 to the oxidizer GAs exhaust path 42. As a result, in the first fuel cell stack 22A, the necessary power generation continues, but the progress of the water discharge process is substantially unchanged.
Although the progress of the drainage treatment in the first fuel cell stack 22A is substantially unchanged, the drainage treatment in the second fuel cell stack 22B eventually progresses to a point where the degree of progress of the drainage treatment in the two fuel cell stacks 22A and 22B becomes equal. That is, the impedance of the first fuel cell stack 22A reaches the predetermined value PV (yes in step S10), and the impedance of the second fuel cell stack 22B also reaches the predetermined value PV (yes in step S20).
When "yes" is returned in step S10 and "yes" is returned in step S20, the control device 70 adjusts the first transport flow rate GA and the second transport flow rate GB to the standard flow rate N (step S24). That is, the control device 70 maintains the opening degrees of the inlet valve 36 and the outlet valve 44 at 100% and the opening degree of the split valve 40 at 0% in each of the fuel cell units 20A and 20B (time T2 in fig. 4A and 4B). As a result, after time T2 in fig. 4A and 4B, the drainage process in the fuel cell stacks 22A and 22B is equally performed.
Then, the drainage process further progresses in each of the fuel cell stacks 22A and 22B, and the impedance of both the fuel cell stacks 22A and 22B becomes the termination value FV or higher (yes in step S16). At this time, the control device 70 terminates the drainage process shown in fig. 3 (time T3 in fig. 4A and 4B).
On the other hand, the drainage treatment of the first fuel cell stack 22A may progress relatively slowly, and the drainage treatment of the second fuel cell stack 22B may progress relatively quickly. In this case, only the impedance of the second fuel cell stack 22B reaches the predetermined value PV (no in step S10 and yes in step S12), and the process of step S18 is performed instead of the process of step S22. In step S18, the control device 70 limits the second transport flow rate GB to the second fuel cell stack 22B to a predetermined limiting flow rate N, and maintains the first transport flow rate GA to the first fuel cell stack 22A at the standard flow rate N. Therefore, the second transport flow rate GB is smaller than the first transport flow rate GA. As a result, in the second fuel cell stack 22B, the necessary power generation continues, but the progress of the water discharge process is substantially unchanged.
In the above-described fuel cell system 10, the control device 70 monitors the impedance of each fuel cell stack 22 during the drainage process. The smaller the amount of residual water in the fuel cell stack 22, the higher the impedance detected with respect to the fuel cell stack 22. Therefore, the amount of residual water can be considered to be relatively small inside the fuel cell stack 22 that detects the resistance of not less than the predetermined value PV, and the amount of residual water can be considered to be relatively large inside the fuel cell stack 22 that detects the resistance of less than the predetermined value PV. Therefore, in the water discharge process shown in fig. 3, the flow rate of the air to the first fuel cell stack 22A, the impedance of which has reached the predetermined value, is restricted until the impedance reaches the predetermined value PV for the two fuel cell stacks 22A and 22B (times T1 to T2 in fig. 4A and 4B). Such a configuration enables the amount of residual water in the two fuel cell stacks 22A and 22B to be equalized during the drainage process. Therefore, the drainage process (time T2 in fig. 4A and 4B) that does not limit the flow rate of air delivered to each of the fuel cell stacks 22A and 22B can be resumed, so that the drainage processes of the two fuel cell stacks 22A and 22B are terminated simultaneously (time T3 in fig. 4A and 4B), and thus the difference in the amount of residual water in each fuel cell stack can be made relatively small.
In the above-described embodiment, the delivery flow rates GA and GB of the air, which do not restrict the delivery flow rate in steps S14, S18, S22 and S24 of fig. 3, are equal to the standard flow rate N. In this regard, in another embodiment, the delivery flow rates GA and GB of the air, which do not restrict the delivery flow rate in steps S14, S18, S22 and S24 of fig. 3, may be greater than the standard flow rate N, or may be smaller.
In the above-described embodiment, when the second transport flow rate GB is limited in the drainage process shown in fig. 3, the flow dividing valve 40 of the second fuel cell unit 20B is opened to bypass the air from the flow dividing path 38 to the oxidizer gas exhaust path 42. In this regard, in another embodiment, the second delivery flow rate GB may be limited by limiting the delivery flow rate of air by the compressor 32 of the second fuel cell unit 20B. According to such a configuration, the delivery flow rate of the air supplied to the fuel cell stack 22 can be adjusted regardless of the presence or absence of the above-described split path 38.
As shown in fig. 6A and 6B, the above-described drainage treatment may further include correcting the flow rate of the air to be delivered in accordance with the temperature of each fuel cell stack 22, but is not particularly limited thereto. The speed of progress of the drainage process in the fuel cell stack 22 varies according to the temperature inside the fuel cell stack 22 (specifically, the amount of saturated water vapor). That is, the higher the temperature of the fuel cell stack 22, and thus the greater the amount of saturated water vapor, the faster the drainage process will progress. For example, when the temperature of the second fuel cell stack 22B is lower than that in the first fuel cell stack 22A, the amount of saturated water vapor in the second fuel cell stack 22B is smaller than that in the first fuel cell stack 22A. In this case, by setting the flow rate n+α obtained by adding the corrected flow rate α to the standard flow rate N, the second transport flow rate GB to the second fuel cell stack 22B can be made larger than the first transport flow rate GA to the first fuel cell stack 22A. Therefore, correcting the transport flow rates GA and GB to each fuel cell stack 22 in accordance with the temperature of each fuel cell stack 22 makes it possible to eliminate the difference in the amount of residual water in each fuel cell stack 22 in a relatively short period of time.
Although specific examples are described above in detail, these are merely exemplary and are not intended to limit the scope of the claims. The technology described in the claims includes various modifications and variations of the specific examples illustrated above. The technical elements described in the present specification or illustrated in the drawings represent technical utility alone or in combination.

Claims (5)

1. A fuel cell system comprising:
a plurality of fuel cell stacks electrically connected in series;
a gas supply unit that supplies gas to the plurality of fuel cell stacks;
an impedance detection unit that detects impedances of the plurality of fuel cell stacks; and
a control device that controls operations of the plurality of fuel cell stacks and the gas supply unit, and that obtains a detection value detected by the impedance detection unit, wherein
The control device is configured to perform a water discharge process in which, when power generation of the plurality of fuel cell stacks is stopped, the gas is supplied to the plurality of fuel cell stacks to discharge water remaining in the plurality of fuel cell stacks, and
the drainage treatment includes: for a fuel cell stack in which the detection value of the plurality of fuel cell stacks reaches a predetermined value, the transport flow rate of the gas is restricted until the detection value reaches the predetermined value at all of the plurality of fuel cell stacks.
2. The fuel cell system according to claim 1, wherein the drainage process further includes correcting a transport flow rate of the gas according to temperatures of the plurality of fuel cell stacks.
3. The fuel cell system according to claim 1 or 2, wherein the gas is an oxidant gas supplied to a cathode side of the plurality of fuel cell stacks.
4. The fuel cell system according to claim 3, wherein:
for each of the plurality of fuel cell stacks, the gas supply unit includes:
an oxidant gas supply path connected to a supply port of the fuel cell stack, and including a compressor, an oxidant gas discharge path connected to a discharge port of the fuel cell stack, and
a shunt path that connects the oxidant gas supply path and the oxidant gas discharge path to each other, and that includes a shunt valve; and limiting the flow rate of the oxidizer gas in the wastewater treatment includes: the diverter valve is opened to bypass the oxidant gas from the diverter path to the oxidant gas exhaust path.
5. The fuel cell system according to claim 4, wherein restricting the flow rate of the oxidizer gas in the drainage process includes: limiting the flow rate of the oxidant gas delivered by the compressor.
CN202310662306.2A 2022-08-24 2023-06-06 Fuel cell system Pending CN117638154A (en)

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